A parallel-plate type (capacitively coupled) plasma processing apparatus, an inductively coupled plasma processing apparatus, a microwave plasma processing apparatus, and the like have been used as an apparatus for performing microprocessing, such as etching or film formation, onto a target object to be processed, e.g., a semiconductor wafer (hereinafter, referred to as “wafer”) by plasma.
In the parallel-plate type plasma processing apparatus among these apparatuses, a high frequency power is applied to at least any one of an upper electrode and a lower electrode provided to face each other within a processing chamber and a gas is excited into plasma by electric field energy of the high frequency power. Then, the target object is microprocessed through a plasma process, e.g., an etching process, by the generated electric discharge plasma.
In recent years, for the purpose of improving performance of a plasma process in such a parallel-plate type plasma processing apparatus, there has been suggested a process of applying a DC voltage into a processing chamber by connecting an upper electrode to a DC power supply. In such a plasma processing apparatus, in order to apply a DC voltage to the upper electrode, a surface of a grounded electrode (hereinafter, referred to as “ground electrode”) paired with the upper electrode is exposed within a processing chamber.
However, in some cases, a reaction product generated from a plasma process may be deposited on the exposed surface of the ground electrode, so that a DC current flow between the upper electrode and the ground electrode may be impeded. As a result, it is difficult to appropriately apply a DC voltage into the processing chamber, so that plasma becomes unstable.
Therefore, in order to solve such a problem, for example, Patent Document 1 suggests providing a shield wall around the ground electrode to suppress adhesion of the reaction product caused by the plasma to the ground electrode.